#version 410 core
// Interpolated values from the vertex shaders
in vec3 fragmentColor;
in vec3 Position_worldspace;
in vec3 Normal_cameraspace;
in vec3 EyeDirection_cameraspace;
in vec3 LightDirection_cameraspace;
in vec2 UV;

// Ouput data
out vec3 color;

// Values that stay constant for the whole mesh.
uniform mat4 MV;
uniform vec3 LightPosition_worldspace;
uniform sampler2D myTexture;

void main(){

// Light emission properties
// You probably want to put them as uniforms
vec3 LightColor = vec3(0.15,0.15,0.15);
float LightPower = 80.0f;

// Material properties
vec3 MaterialDiffuseColor = texture(myTexture, UV ).rgb;
vec3 MaterialAmbientColor = vec3(0.6,0.6,0.6) * MaterialDiffuseColor;
vec3 MaterialSpecularColor = vec3(0.2,0.2,0.2);

// Distance to the light
float distance = length( LightPosition_worldspace - Position_worldspace );

// Normal of the computed fragment, in camera space
vec3 n = normalize( Normal_cameraspace );
// Direction of the light (from the fragment to the light)
vec3 l = normalize( LightDirection_cameraspace );
// Cosine of the angle between the normal and the light direction,
// clamped above 0
//  - light is at the vertical of the triangle -> 1
//  - light is perpendicular to the triangle -> 0
//  - light is behind the triangle -> 0
float cosTheta = clamp( dot( n,l ), 0,1 );

// Eye vector (towards the camera)
vec3 E = normalize(EyeDirection_cameraspace);
// Direction in which the triangle reflects the light
vec3 R = reflect(-l,n);
// Cosine of the angle between the Eye vector and the Reflect vector,
// clamped to 0
//  - Looking into the reflection -> 1
//  - Looking elsewhere -> < 1
float cosAlpha = clamp( dot( E,R ), 0,1 );

color =
// Ambient : simulates indirect lighting
MaterialAmbientColor +
// Diffuse : "color" of the object
MaterialDiffuseColor * LightColor * LightPower * cosTheta / (distance*distance) +
// Specular : reflective highlight, like a mirror
MaterialSpecularColor * LightColor * LightPower * pow(cosAlpha,5) / (distance*distance);

}